I also received the 25,000 Marriott Rewards bonus points when you stay a total of 15 VisaŽ-paid nights at Marriott offer. ^
FWIW, for those that do not yet see the MegaBonus offer, the FAQ states the following:
Do stays made prior to registration count toward the promotion?
Yes, as long as you register during the promotion time frame of September 11, 2007 through January 18, 2008 and your previous stays are between September 23, 2007 and January 18, 2008.
This leads me to believe that since the offical registration start date isn't until Sep 11, they may well be loading these offers during nightly batch processing and many have not yet been loaded. I would be patient and hopefully an offer will appear by Sep 11. I am also going to go back after the 11th and try to reregister since the FAQ indicates that you cannot register until then.